1. Field of the Invention
The invention relates to a photodetector apparatus, particularly to a quantum dot infrared photodetector apparatus.
2. Description of the Prior Art
In recent years, there are many researches associated with the development of quantum dot infrared photodetector, because it has the characteristics of low cost and high-temperature operation etc. The basic function of quantum dot infrared photodetector has been improved, and its performance has also been increased greatly.
Conventionally, quantum dot means that the nano-grade semiconductor raw materials having the narrower energy gap are imbedded into the semiconductor materials having the wide energy gap to form the quasi-zero-dimensional nano-material. The transitions of electrons among different states can be restrained by the quasi-zero-dimensional degree of freedom for electron state. Therefore,the quantum dot infrared photodetector formed by the quantum dot has the characteristics of low dark current, high responsivity and high-temperature operation etc.
In addition, the quantum dot infrared photodetector can absorb normal incident infrared due to three-dimensional bound states. The quantum dot infrared photodetector has the advantage of simplified manufacturing process compared to the quantum well infrared photodetector (QWIP) which cannot absorb normal incident light. And it is advantageous for the manufacturing of medium-wavelength (3 μm to 5 μm) photodetector because of larger energy gap difference of quantum dot structure. Thus, the development of quantum dot infrared photodetector is attracted a lot of interest by people. As for the quantum dot infrared photodetector technology, it was disclosed in “Applied Physics Letter 73, 963 (1998)” and “Applied Physics Letter 73, 3153 (1998)” These two prior papers disclosed the basic structure and embodiments of quantum dot infrared photodetector technology. Even the basic concept of quantum dot infrared photodetector technology had been revealed earlier in 1996, such as in the “Semiconductor Science Technology 11, 759 (1996)”. It was also much earlier compared to the first patent disclosing quantum dot infrared photodetector technology as U.S. Pat. No. 6,239,449 “Quantum dot infrared photodetectors (QDIP)”.
The early quantum dot infrared photodetector technology was limited by self-assembled quantum dot process. Thus, in order to solve the adjustment problem of the detecting wavelength, the dots-in-a-well structure was disclosed in “Applied Physics Letter 79, 3341 (2001)”. In the dots-in-a-well structure, the thickness of quantum well could be employed to change the detecting wavelength, which was advantageous for the application of quantum dot infrared photodetector. However, the addition of quantum well structure would influence the quantum efficiency of the component.
Because of the above-mentioned reasons, the development of quantum dot infrared photodetector has been paid more attention day by day. In order to respond the future demand of photodetector technology, it is necessary to develop relevant technology of infrared photodetector, to reduce the manufacturing cost, manpower and time, and achieve the purpose of energy saving and carbon reduction effectively.